Some conventional data storage systems include two power supplies and two storage processors for fault tolerance. Each power supply has enough capacity for both storage processors. Accordingly, if one power supply fails, the other power supply is capable of powering both storage processors and thus enabling the data storage system to continue operation (e.g., the storage processors can transition from a write-back caching mode to a write-through caching mode to ensure safe storage of data).
Similarly, each storage processor is capable of performing data storage operations independently of the other. Accordingly, if one storage processor fails, the other storage processor can continue to perform data storage operations so that the data storage system as a whole remains operational, e.g., the remaining storage processor can either (i) write cached data to non-volatile memory (e.g., magnetic disk storage, backup power supplied semiconductor memory, etc.) and then perform a graceful shutdown, or (ii) transition to a write-through caching mode and thus continue operation without the risk of losing data.
For additional fault tolerance, each power supply typically includes sensing circuits (e.g., an airflow sensor, a temperature sensor, etc.) that causes that power supply to perform a fault tolerant procedure upon detection of a detrimental condition. For example, upon detection of an over-temperature condition, a power supply can send an error signal to the storage processors directing the storage processors to dump the cache out to non-volatile memory and then safely shutdown.